The present invention relates to a clean room environment analysis system and to an analysis method using same. More particularly, the present invention relates to a system for analyzing water-soluble contaminants present in the air of a clean room.
It is well known that the quality and yield of semiconductor devices are greatly affected by the ambient conditions under which they are manufactured. Accordingly, manufacturing processes for semiconductor devices are performed in cleanrooms having highly-purified environments in which various kinds of air contaminants, such as dust, microscopic organisms, ion particles, etc., must be eliminated to the greatest, practical degree possible. This is especially true for those clean room fabrication processes which form highly-sophisticated patterns on semiconductor devices. Unfortunately, in actual practice, the air in cleanrooms always contains some contaminants, and these contaminants create wafer defects. Thus, techniques for controlling air quality in cleanrooms have become increasingly important as semiconductor geometries have become increasingly small.
Water-soluble contaminants, such as ammonia, nitric acid compounds, sulfuric acid compounds and the like, are particularly troublesome. These water-soluble contaminants are generated when various semiconductor compounds, gases, or other contamination sources come into contact with moisture in the air. These contaminants typically have ionic bonds, and are thus easily attached to the surface of a semiconductor device under manufacture. Water-soluble contaminants, along with other contaminants, create a "haze" phenomenon over the surface of a semiconductor wafer. Haze causes deterioration in photoresist layers, and during diffusion processes may act as undesired dopants.
As a result of these problems, which are merely selected examples, various conventional analysis systems and methods for analyzing water-soluble contaminants found in clean room air have been developed in previous attempts to control water-soluble contaminants. One widely used method is the "Jar Test." In the Jar test, a jar filled with deionized water is left in the clean room. Over time, particles are absorbed into the deionized water. Subsequently, the "contaminated" deionized water is analyzed to roughly determine the nature and content of clean room contaminants. Another conventional method is the "Impinger Method," in which some portion of the clean room air is forcibly circulated and passed through deionized water. As with the Jar Test, the resulting contaminated water may be evaluated.
These conventional methods for capturing water soluble contaminants are simple and easily employed. Unfortunately, it takes a long time for sufficient contamination particles to be captured for evaluation. The length of time required to capture sufficient water-soluble contaminants in conventional methods creates evaluation inaccuracies. Further, contamination evaluation is done after-the-fact, rather than in real-time. This precludes the identification of transient clean room contamination phenomenon, the accurate development of short-term evaluation criteria, and the recognition of absolute contaminant concentration relationships with other factors such a time.